Improvement in illuminating vault-covers



UNITED STATES PATENT QFFIGE.

JOSHUA K. INGALLS, OF STARKEY, NEW YORK.

IMPROVEMENT IN ILLUMINATI-NG VAULT-COVERS.

Specification forming part of Letters Patent No. 146,074, dated December30, 1873 application filed September 20, 1871.

To all whom it may concern:

Be it'known that I, JOSHUA K. INGALLS, of Starkey, Yates county, in theState of New York, have invented an Improvement in Illuminating-Platesfor Covering Vaults, Areas, &c., of which the following is aspecification:

In vault-covers and illuminating-plates, as heretofore'used, theglasses, which have been mainly made of a circular form, have beenprotected from breakage and abrasion by knobs placed in the triangularspaces formed by the arrangement of the apertures in which the glassesare set. These knobs have usually been made of a cylindrical or conicalform. Their surfaces presented to the foot are neces sarily small, andhence uncomfortable to walk upon, especially for ladies with lightshoes; and these knobs, while they increase the weight of the plate, donot add to its strength, since the angles in which they are placed arealready far stronger than the narrow web which separates the glasseswhere they approach nearest to each other; and experience has abundantlyshown that, whenever a plate is broken by excessive load, or by unequalshrinkage of the metal, it is through these narrow parts, where theapproach of the apertures to each other and to the edge of the plateleaves the smallest proportion of metal.

My invention has for its object to obviate these defects and consists inso arranging knobs or protuberances as to strengthen the plate at itsweakest points, and afford better protection to the glasses, and also tofurnish a surface better adapted for walking upon.

Figure 1 is a plan of an illuminating-plate embodying my improvement.Fig. 2 is a vertical section, showing the arrangement of the protectingparts through line w w of Fig. 1.

As represented in the drawing, A indicates the plate or grating, whichis preferably made of cast metal, and of such size and strength as tobest adapt it to the space which it is intended to cover. This plate isprovided with a series of perforations, which receive the glass disks orlenses B B, which are supported by a seat, and secured by a filling ofcement or metallic packing. The lenses are preferably arranged intriangular order, to economize space,

guard or protuberance, c, rising above the general surface, and situatedbetween the lenses.

at their point of nearest approach. The repetition of this protuberanceon each of the intervenin g bars or webs c 0 forms, apparentlyowing tothe arrangement of the glasses-a. border, consisting of six elongatedknobs surrounding each lens, which aifords adequate protection to theglasses, being elevated above their level, and gives sufficient extentof surface to be trodden' upon without discomfort to the feet.

By increasing the depth or thickness of the web or bars in this manner,the metal is so disposed as to increase the strength where most requiredwithout materially adding to the weight of the plate, or diminishing thesize or number of the apertures for illumination, while, at the sametime, the protuberances are brought in close proximity to the glass, andmore effectual protection is obtained.

It is obvious that the same resultswould be obtained in an arrangementof the illuminating-orifices in a rectangular order, or with ap erturesfor illuminating of an oblong form, provided the protuberances are soarranged as to surround, or nearly so, the lenses or glasses, and tooccupy the weakest intervening portions of the plate, being the pointswhere the lenses approach most nearly to one another.

I claim In combination with a vault-cover, the ribs or protuberances c earranged to surround, or

partially surround, the lenses B B, for strengthening the iron plate andforming a better surface for walking upon, substantially as set forth.

In witness whereof I have hereunto signed my name in the presence of twosubscribing

